A dual mode mobile terminal refers to a mobile terminal capable of supporting two types of wireless communications protocols. The dual mode mobile terminal is mainly used in an area whether heterogeneous communication networks coexist. As a representative example of the dual mode mobile terminal, a mobile terminal available for both LTE wireless communication and CDMA wireless communication is very popular. Although a dual mode mobile terminal capable of communicating with both LTE network and CDMA network are taken as an example for the present invention, it is apparent to those skilled in the art that the present disclosure is applicable to other species of wireless communication systems.
In the LTE wireless communication, a multiple input multiple output or MIMO scheme for transmitting and receiving signals using a plurality of transmitting antennas and a plurality of receiving antennas is adopted. Once the MIMO scheme is adopted, a transmitting or receiving stage is able to increase capacity and enhance performance using a plurality of antennas. Moreover, the CDMA wireless communication utilizes multiple antennas for diversity scheme since EV-DO REV. A. In this disclosure, MIMO is indicative of the use of more than one antennas.
In order to receive one whole message, MIMO system does not depend on a single antenna path. Instead, in the MIMO system, data is completed by collecting and combining data fragments received via plural antennas together. If the MIMO system is used, data rate can be improved within a cell area having a specified size. System coverage may be also improved, while securing a specific data rate. Moreover, the MIMO system is widely applicable to a mobile communication terminal, a relay and the like. According to the MIMO system, it is able to overcome the limited transmission traffic in mobile communication of the related art having used a single antenna.
Meanwhile, in a dual mode terminal of the related art, it may cause a problem that transmission/reception of LTE signals is interrupted in a specific situation due to the limitation put on the number of antennas loadable in one terminal device. FIG. 1 is a diagram for explaining a problem that may be caused by a general dual mode terminal.
Referring to FIG. 1, when a terminal, that is communicating with an LTE network, attempts switch to communicate with a CDMA network, it stops receiving LTE signal from a base station (eNodeB) and then measures the quality of the available CDMA signal. In this case, the quality of the CDMA signal is measured based on eHRPD (enhanced high-rate packet data) which is a new version of 1xEV-DO upper layer protocol stack developed by 3GPP2 Standard committee to prepare for the wireless communication network interoperability with LTE.
The time spent to do the CDMA signal quality measurement is referred to as a measurement gap. This measurement gap is the length of interruption of reception/transmission of LTE signal. The frequency efficiency of the LTE suffers if the measurement gap is long.